In the construction industry, structures can be coated with passive fireproofing material. Fireproofing material is known to provide fire resistance to substrates susceptible to fire, such as steel elements of buildings including beams, columns, roofs, decks, floors and plates and the like. These materials include spray applied fire resistant materials (SFRMs) which can be used for direct application to structural steel building members. They are predominantly cementitious or plaster-based. Their fire-resistive qualities and physical characteristics can vary widely between the respective types of SFRM. For example, the density of SFRMs are lower than normal weight concrete (e.g., 140-150+ lbs/ft3) and light weight concrete (e.g., 90-115 lbs/ft3, 90-150 lbs/ft3). Because SFRMs are made with light weight coarse aggregates, such as exfoliated vermiculite, mica, low density polystyrene etc., the materials can be very porous. In-place density of the SFRMs can be low (e.g., 15-60 lbs/ft3, 15-70 lbs/ft3).
SFRMs can consist of inorganic binders such as plaster or Portland cement, and various fillers such as vermiculite, mica, limestone, gypsum, lightweight polystyrene beads, mineral wool, glass fibers, ceramic fibers, aluminum ore, clay and quartz. Examples of Portland-cement-based fireproofing products are Fendolite® MII from Isolatek International, Pyrocrete® 241 from Carboline and Monokote® Type Z-146 from W. R. Grace. Examples of plaster-based fireproofing products are CAFCO® 300 from Isolatek International, Pyrolite® 15 from Carboline and Monokote® MK-6 from W. R. Grace. SFRMs differ from concretes in both density and components, e.g., normal concrete can include cement, sand and aggregates/lightweight concrete can include cement, sand and lightweight aggregates.
Due to the low in-place density and porosity of SFRMs, large voids in the interior structure can be present and create pathways for intrusions by water and chemicals, such as salts, fertilizers, etc. Accelerated by water, the intrusions can incur several types of damages, such as freeze-thaw disintegration, alkali-aggregate reaction, sulfate attack, carbonation and corrosion of the underlying substrate (e.g., steel). Consequently, the SFRMs, the underlying substrate or both can be damaged and lose their fire resistant property or structural integrity.
Water repellent additives have been incorporated into concrete serving to aid in the resistance to moisture, such as rain water, from penetrating excessively into the concrete. To date, these types of materials have not been incorporated into SFRMs. For one reason, the application methodology of SFRMs does not lend SFRMs to include water repellent components. Also, there is uncertainty in the industry regarding the compatibility of concrete additive in other materials. Although both SFRM and concrete contain significant amounts of Portland cement, the two classes of product commonly show different properties with respect to additives. Water repellent additives used in concrete are not indicated for SFRMs due to the differences in application, requirements and different effects of common additives. Concrete is normally applied by precasting or casting in place. SFRMs are normally applied by spraying onto structural steel members through a hose under 30-80 psi air pressure. To be effective the SFRM requires good pumpability, good hangability, proper stability and set times, strong adhesion on the substrate, or combinations thereof. In some embodiments, the SFRM exhibits all of these properties.
Moreover, the effects of different additives in both concrete and SFRMs are not similar. For example, the addition of a superplasticizer in concrete allows for the use of less water and increases the concrete's physical strength. The use of a superplasticizer in a SFRM often results in a decrease in the SFRM's physical strength. Similarly, the use of a shrinkage reducing agent can reduce shrinkage in concrete but not in a SFRM. The use of silica fume fillers in concrete produces increased physical strength. In a SFRM silica fume fillers also increase physical strength. But, they also significantly reduce set time (resulting in problems with pump-ability and spray-ability), reduce adhesion (to the point of delamination) and increase shrinkage (which can lead to cracking). Finally, the use of Class C fly ash in concrete reduces shrinkage and increases physical strength. In a SFRM, however, Class C fly ash increases shrinkage and reduces adhesion (to the point of delamination).
The present disclosure is directed to a spray applied fire resistant material having water repellent agents, latex, and combinations thereof to reduce or eliminate water damage of the SFRM and the SFRM coated substrate.